As an output voltage control apparatus of a generator, an automatic voltage regulator for an alternating-current generator is known which has a generator winding and an excitation winding wound to a stator side, a field winding wound around a rotor rotated by a drive source, and a rectifier for rectifying a current generated to the excitation winding and supplying the rectified current to the field winding and keeps a voltage output from the generator winding to a preset voltage by controlling a current supplied to the excitation winding as shown in, for example, Patent Literature 1.
In this kind of the output voltage control apparatus, as a technique for improving a distortion of a waveform of an output voltage waveform from a generator winding, an output waveform is designed near a sine wave by adjusting the number of windings of respective slots of a stator winding for the purpose of a waveform improvement, and a skew and a brake winding are applied.
As shown in, for example, Patent Literature 2, the skew means a shape of electromagnetic steel sheets stacked in a state that slots or a rotor is twisted for the purpose of improving a torque ripple as a motor and a waveform as a generator in a synchronous machine, an induction machine, and the like. The application of the skew has an effect of reducing a torque ripple and improving a waveform of a generated voltage by suppressing a steep change of a magnetic flux in linkage with a winding.
As shown in, for example, Patent Literature 3, the brake winding means a winding formed in such a manner that several slots having the same shape are disposed to a rotor magnetic pole at equal intervals, conductor bars such as copper bars or brass bars having the same shape are inserted into the slots, and both the ends of the conductor bars are brazed to short-circuit rings. Although the brake winding is disposed to a silent-magnetic-pole iron core of a silent-pole type rotary generator for the purpose of hunting prevention, cancellation of reverse phase fractional current, and the like, a voltage waveform can be improved by disposing the brake winding by offsetting it from a center of the silent-magnetic-pole iron core.